The Pulse

Bowel cancer: early detection is vital

Bowel cancer is our second biggest cancer killer, but if it's detected early your survival odds are good. So what's the best way to catch it early?

Published 08/09/2010

[Image source: iStockphoto]

You've probably seen the pink ribbons for breast cancer, blue ribbons for prostate cancer and even the pearl ribbons for lung cancer; but have you ever seen a ribbon for bowel cancer?

While a ribbon may not jolt us out of complacency, we need something to make us more aware of bowel cancer. It's our second biggest cancer killer, after lung cancer.

Each year around 4,000 Australians die from bowel cancer (also known as colorectal cancer) and 13,500 are diagnosed with it, making it our most common internal cancer.

It occurs in the large bowel  in either the colon or rectum  and develops from small growths on the bowel lining called polyps, although not all polyps will become cancerous.

But your chances of recovering from bowel cancer are better than for many other cancers if you catch it early enough. This is why there is a growing push for a better national screening program, and why we have been taught to look out for certain bowel cancer symptoms.

However, new research suggests that some of the symptoms we associate with bowel cancer may not be as helpful in identifying the disease as previously thought.

Bowel cancer symptoms

The research from the University of Sydney and the Concord Repatriation General Hospital, published in Alimentary Pharmacology and Therapeutics, surveyed more than 8,000 people who had been referred for a colonoscopy (a procedure that involves a small camera being inserted into the bowel to check for polyps and other changes).

Participants gave details of their symptoms, their medical history and other basic information, such as age and gender. The researchers then looked at which symptoms were associated with bowel cancer.

Rectal bleeding, a change in your bowel habit, and the presence of rectal mucus were all strongly associated  especially if these symptoms had occurred at least weekly and for less than one year. (Anaemia, fatigue and weight loss of more than six kilograms were also associated with bowel cancer. But because these symptoms are also common to other cancers, they are known as "non-specific symptoms".)

However, the researchers found some symptoms that had previously been considered "red flags" for bowel cancer  such as abdominal pain, abdominal or anal lump, anal pain, and a sense of urgency to pass a bowel motion  were actually not as reliable as thought.

In fact, symptoms on the whole were not found to be as good indicators of bowel cancer as once believed, says Dr Barbara-Ann Adelstein, one of the researchers and now a Clinical Research Fellow at the Prince of Wales Hospital Clinical School.

Other factors, such as age and medical history, are better predictors of bowel cancer risk than any of the symptoms. Adelstein says.

The researchers found that a model in which symptoms are combined with medical history and other factors, such as age and gender, was a good way for people to be divided into risk categories.

But this doesn't mean that you should ignore bowel symptoms, even those not associated with bowel cancer. However, knowing which symptoms are most significant could reduce worry around those less significant symptoms, says Adelstein.

She says when it comes to bowel symptoms, even ones associated with cancer, the best attitude to have is not "Have I got bowel cancer?" but "I have a symptom that I would like to be investigated".

Colonoscopy

Other experts say it's better to find polyps in the bowel before they start causing symptoms.

"Waiting for symptoms in relation to bowel cancer is not the way to go in this day and age," says Professor Graham Newstead, a colorectal surgeon at the Prince of Wales Private Hospital and executive director of the Colorectal Surgical Society of Australasia.

This is because, unlike other cancers, bowel cancer is preventable, Newstead says. And the reason for this, is that colonoscopies allow polyps to be identified and removed before they have the chance to become cancerous.

Often by the time someone is experiencing symptoms, their bowel cancer is advanced. So identifying important symptoms is a little like "closing the stable door after the horse has bolted," he says.

Screening

This is why bowel cancer screening is so important, both Newstead and Adelstein say.

The screening tool is a Faecal Occult Blood Test (FOBT), which detects tiny amounts of blood in the faeces that could be leaking from a bowel tumour or polyp (though the blood could be associated with other conditions, such as haemorrhoids, too). You can do the test at home and then send your sample away to be checked; if your result is positive then you are sent off for a colonoscopy.

Currently, the FOBT is being sent to people turning 50 between January 2008 and December 2010, and those turning 55 or 65 between July 2008 and December 2010.

But this approach has been criticised because it only offers the FOBT as 'one off' and doesn't provide repeat testing at regular intervals. Also it doesn't cover everyone at risk, particularly people over 65, who are more at risk (bowel cancer risk increases with age).

Studies in other countries have shown that screening people between the ages of 50 and 74 every two years with FOBTs reduces bowel cancer deaths by around one quarter.

Local cancer experts would also like to see screening for everyone over 50 every two years. (If you're deemed to be at higher risk of bowel cancer however - say because you have a family history of the disease - the National Health and Medical Research Council guidelines recommend you be offered a colonoscopy every five years after 50, or younger depending on your medical history.)

But ongoing funding for even the existing screening program is uncertain. This has been criticised, given that national breast and cervical cancer screening programs have been in place for many years, yet the annual death toll from these two cancers is less than for bowel cancer.

Nonetheless, Newstead stresses screening is vital and says if you're over 50, you should talk to your doctor about your screening options. (Quite apart from the screening program where people are automatically sent FOBTs, you can buy the test from the chemist and there is a Medicare rebate available to help cover the costs.) You certainly should not rely on being able to identify symptoms and you should not think you don't need to be screened just because you don't have symptoms, he says.